Revert 239894 "Linux Sandbox: check no threads before fork()."

BUG=327241, 328249

> Linux Sandbox: check no threads before fork().
> 
> Always check that no threads are running before fork().
> 
> BUG=327241
> NOTRY=true
> 
> Review URL: https://codereview.chromium.org/108173008

TBR=jln@chromium.org

Review URL: https://codereview.chromium.org/106903012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@240670 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed